libcxx/include/__algorithm/ranges_min_element.h

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef _LIBCPP___ALGORITHM_RANGES_MIN_ELEMENT_H
  10 #define _LIBCPP___ALGORITHM_RANGES_MIN_ELEMENT_H
  11
  12 #include <__config>
  13 #include <__functional/identity.h>
  14 #include <__functional/invoke.h>
  15 #include <__functional/ranges_operations.h>
  16 #include <__iterator/concepts.h>
  17 #include <__iterator/projected.h>
  18 #include <__ranges/access.h>
  19 #include <__ranges/concepts.h>
  20 #include <__ranges/dangling.h>
  21 #include <__utility/forward.h>
  22
  23 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  24 #  pragma GCC system_header
  25 #endif
  26
  27 #if _LIBCPP_STD_VER >= 20
  28
  29 _LIBCPP_BEGIN_NAMESPACE_STD
  30
  31 namespace ranges {
  32
  33 // TODO(ranges): `ranges::min_element` can now simply delegate to `std::__min_element`.
  34 template <class _Ip, class _Sp, class _Proj, class _Comp>
  35 _LIBCPP_HIDE_FROM_ABI constexpr _Ip __min_element_impl(_Ip __first, _Sp __last, _Comp& __comp, _Proj& __proj) {
  36   if (__first == __last)
  37     return __first;
  38
  39   _Ip __i = __first;
  40   while (++__i != __last)
  41     if (std::invoke(__comp, std::invoke(__proj, *__i), std::invoke(__proj, *__first)))
  42       __first = __i;
  43   return __first;
  44 }
  45
  46 namespace __min_element {
  47 struct __fn {
  48   template <forward_iterator _Ip,
  49             sentinel_for<_Ip> _Sp,
  50             class _Proj                                             = identity,
  51             indirect_strict_weak_order<projected<_Ip, _Proj>> _Comp = ranges::less>
  52   _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr _Ip
  53   operator()(_Ip __first, _Sp __last, _Comp __comp = {}, _Proj __proj = {}) const {
  54     return ranges::__min_element_impl(__first, __last, __comp, __proj);
  55   }
  56
  57   template <forward_range _Rp,
  58             class _Proj                                                         = identity,
  59             indirect_strict_weak_order<projected<iterator_t<_Rp>, _Proj>> _Comp = ranges::less>
  60   _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr borrowed_iterator_t<_Rp>
  61   operator()(_Rp&& __r, _Comp __comp = {}, _Proj __proj = {}) const {
  62     return ranges::__min_element_impl(ranges::begin(__r), ranges::end(__r), __comp, __proj);
  63   }
  64 };
  65 } // namespace __min_element
  66
  67 inline namespace __cpo {
  68 inline constexpr auto min_element = __min_element::__fn{};
  69 } // namespace __cpo
  70 } // namespace ranges
  71
  72 _LIBCPP_END_NAMESPACE_STD
  73
  74 #endif // _LIBCPP_STD_VER >= 20
  75
  76 #endif // _LIBCPP___ALGORITHM_RANGES_MIN_ELEMENT_H